Microformats: More Meaning from Your Markup [HTML & XHTML Tutorials]
Great article from Brian ranging from introducing microformats right up to the current state of play.
XFN encoding, extraction, and visualizations - Opera Developer Community
Brian has written an excellent article that not only explains how to write XFN but also how to parse it.
Related links
12 Days of Web
All twelve are out, and all twelve are excellent deep dives into exciting web technologies landing in browsers now.